So this may finally come into play.
Qualcomm had a job listing mentioning Surface and Xbox portfolio built on Qualcomm chips.
With the GDK having native ARM64 support. MS would be in position to do a first party handheld using Qualcomm rather than AMD AT4 which is what the other Windows handhelds will use. Jez said they put it on hold but not given up.
Qualcomm is also very willing to give their chips for dirt cheap compared to AMD or Intel. It was reported that the Snapdragon Elite Plus in a Surface 11 was $150, and Elite X was $220, including the LTE module. Qualcomm wants to take market share. A Windows on ARM64 first party Xbox handheld wouldn't need to generate profit like the OEMs, and no licensing fees.